Field of the Invention PA1 Description of the Prior Art PA1 System Overview PA1 Machine Description PA1 Master/Area Communication System PA1 MACS Optical Link PA1 MACS I/O Instructions and Operational Overview PA1 Table I PA1 Simultaneous Area Operation PA1 Status Read and Write Commands PA1 TABLE 2 PA1 TABLE 3 PA1 TABLE 4 PA1 Master Controller PA1 Master I/O Interface PA1 Parity Generator PA1 Clock Generator PA1 Shift Controls PA1 Address Decoder PA1 Status Input and Output Control PA1 Interrupt Flip-Flop PA1 Area I/O Interface PA1 Area Controller Operation PA1 Port Structure PA1 Area Microprocessor and Interface PA1 Pseudo-Interrupt Operation PA1 TABLE 5 PA1 TABLE 5A PA1 Machine Clock Interrupt PA1 Real Time Interrupt PA1 Software Description and Organization PA1 State Checker PA1 TABLE 6 PA1 Interrupt Handler PA1 Paper Path Area Controller PA1 TABLE 7 PA1 RDH/ADF Control Console-Controller 8 PA1 TABLE 8 PA1 RDH/Platen Servos-Controller 10 PA1 TABLE 9 PA1 Master/Servo Software Communications PA1 TABLE 10 PA1 Phase Lock Loop Control PA1 Servo Controller Software PA1 Process Controller 12 PA1 Master/PCR Software Communication PA1 TABLE 11 PA1 TABLE 12 PA1 PCR Software